Interleukin-10 and Small Molecule SHIP1 Allosteric Regulators Trigger Anti-inflammatory Effects through SHIP1/STAT3 Complexes.

The anti-inflammatory actions of interleukin-10 (IL10) are thought to be mediated primarily by the STAT3 transcription factor, but pro-inflammatory cytokines such as interleukin-6 (IL6) also act through STAT3. We now report that IL10, but not IL6 signaling, induces formation of a complex between STAT3 and the inositol polyphosphate-5-phosphatase SHIP1 in macrophages. Both SHIP1 and STAT3 translocate to the nucleus in macrophages. Remarkably, sesquiterpenes of the Pelorol family, which we previously described as allosteric activators of SHIP1 phosphatase activity, could induce SHIP1/STAT3 complex formation in cells and mimic the anti-inflammatory action of IL10 in a mouse model of colitis. Using crystallography and docking studies we identified a drug-binding pocket in SHIP1. Our studies reveal new mechanisms of action for both STAT3 and SHIP1 and provide a rationale for use of allosteric SHIP1-activating compounds, which mimic the beneficial anti-inflammatory actions of IL10. VIDEO ABSTRACT.

Interleukin-10 Induces Expression of Neuroendocrine Markers and PDL1 in Prostate Cancer Cells.

Interleukin-10 (IL10) is best studied for its inhibitory action on immune cells and ability to suppress an antitumour immune response. But IL10 also exerts direct effects on nonimmune cells such as prostate cancer epithelial cells. Elevated serum levels of IL10 observed in prostate and other cancer patients are associated with poor prognosis. After first-line androgen-deprivation therapy, prostate cancer patients are treated with androgen receptor antagonists such as enzalutamide to inhibit androgen-dependent prostate cancer cell growth. However, development of resistance inevitably occurs and this is associated with tumour differentiation to more aggressive forms such as a neuroendocrine phenotype characterized by expression of neuron specific enolase and synaptophysin. We found that treatment of prostate cancer cell lines in vitro with IL10 or enzalutamide induced markers of neuroendocrine differentiation and inhibited androgen receptor reporter activity. Both also upregulated the levels of PDL1, which could promote tumour survival in vivo through its interaction with the immune cell inhibitory receptor PD1 to suppress antitumour immunity. These findings suggest that IL10's direct action on prostate cancer cells could contribute to prostate cancer progression independent of IL10's suppression of host immune cells.

Interleukin-10 control of pre-miR155 maturation involves CELF2.

The anti-inflammatory cytokine interleukin-10 (IL10) is essential for attenuating inflammatory responses, which includes reducing the expression of pro-inflammatory microRNA-155 (miR155) in lipopolysaccharide (LPS) activated macrophages. miR155 enhances the expression of pro-inflammatory cytokines such as TNFα and suppresses expression of anti-inflammatory molecules such as SHIP1 and SOCS1. We previously found that IL10 interfered with the maturation of pre-miR155 to miR155. To understand the mechanism by which IL10 interferes with pre-miR155 maturation we isolated proteins that associate with pre-miR155 in response to IL10 in macrophages. We identified CELF2, a member of the CUGBP, ELAV-Like Family (CELF) family of RNA binding proteins, as protein whose association with pre-miR155 increased in IL10 treated cells. CRISPR-Cas9 mediated knockdown of CELF2 impaired IL10's ability to inhibit both miR155 expression and TNFα expression.

Interleukin-10 contributes to PGE2 signalling through upregulation of EP4 via SHIP1 and STAT3.

Macrophage cells form part of our first line defense against pathogens. Macrophages become activated by microbial products such as lipopolysaccharide (LPS) to produce inflammatory mediators, such as TNFα and other cytokines, which orchestrate the host defense against the pathogen. Once the pathogen has been eradicated, the activated macrophage must be appropriately deactivated or inflammatory diseases result. Interleukin-10 (IL10) is a key anti-inflammatory cytokine which deactivates the activated macrophage. The IL10 receptor (IL10R) signals through the Jak1/Tyk2 tyrosine kinases, STAT3 transcription factor and the SHIP1 inositol phosphatase. However, IL10 has also been described to induce the activation of the cyclic adenosine monophosphate (cAMP) regulated protein kinase A (PKA). We now report that IL10R signalling leads to STAT3/SHIP1 dependent expression of the EP4 receptor for prostaglandin E2 (PGE2). In macrophages, EP4 is a Gαs-protein coupled receptor that stimulates adenylate cyclase (AC) production of cAMP, leading to downstream activation of protein kinase A (PKA) and phosphorylation of the CREB transcription factor. IL10 induction of phospho-CREB and inhibition of LPS-induced phosphorylation of p85 PI3K and p70 S6 kinase required the presence of EP4. These data suggest that IL10R activation of STAT3/SHIP1 enhances EP4 expression, and that it is EP4 which activates cAMP-dependent signalling. The coordination between IL10R and EP4 signalling also provides an explanation for why cAMP elevating agents synergize with IL10 to elicit anti-inflammatory responses.

SEMA3C drives cancer growth by transactivating multiple receptor tyrosine kinases via Plexin B1.

Growth factor receptor tyrosine kinase (RTK) pathway activation is a key mechanism for mediating cancer growth, survival, and treatment resistance. Cognate ligands play crucial roles in autocrine or paracrine stimulation of these RTK pathways. Here, we show SEMA3C drives activation of multiple RTKs including EGFR, ErbB2, and MET in a cognate ligand-independent manner via Plexin B1. SEMA3C expression levels increase in castration-resistant prostate cancer (CRPC), where it functions to promote cancer cell growth and resistance to androgen receptor pathway inhibition. SEMA3C inhibition delays CRPC and enzalutamide-resistant progression. Plexin B1 sema domain-containing:Fc fusion proteins suppress RTK signaling and cell growth and inhibit CRPC progression of LNCaP xenografts post-castration in vivo SEMA3C inhibition represents a novel therapeutic strategy for treatment of advanced prostate cancer.

Transfecting RAW264.7 Cells with a Luciferase Reporter Gene.

Transfection of desired genetic materials into cells is an inevitable procedure in biomedical research studies. While numerous methods have been described, certain types of cells are resistant to many of these methods and yield low transfection efficiency(1), potentially hindering research in those cell types. In this protocol, we present an optimized transfection procedure to introduce luciferase reporter genes as a plasmid DNA into the RAW264.7 macrophage cell line. Two different types of transfection reagents (lipid-based and polyamine-based) are described, and important notes are given throughout the protocol to ensure that the RAW264.7 cells are minimally altered by the transfection procedure and any experimental data obtained are the direct results of the experimental treatment. While transfection efficiency may not be higher compared to other transfection methods, the described procedure is robust enough for detecting luciferase signal in RAW264.7 without changing the physiological response of the cells to stimuli.

Interleukin-10 inhibits lipopolysaccharide induced miR-155 precursor stability and maturation.

The anti-inflammatory cytokine interleukin-10 (IL-10) is essential for attenuating the inflammatory response, which includes reducing the expression of pro-inflammatory microRNA-155 (miR-155) in lipopolysaccharide (LPS) activated macrophages. miR-155 enhances the expression of pro-inflammatory cytokines such as TNFα and suppresses expression of anti-inflammatory molecules such as SOCS1. Therefore, we examined the mechanism by which IL-10 inhibits miR-155. We found that IL-10 treatment did not affect the transcription of the miR-155 host gene nor the nuclear export of pre-miR-155, but rather destabilized both pri-miR-155 and pre-miR-155 transcripts, as well as interfered with the final maturation of miR-155. This inhibitory effect of IL-10 on miR-155 expression involved the contribution of both the STAT3 transcription factor and the phosphoinositol phosphatase SHIP1. This is the first report showing evidence that IL-10 regulates miRNA expression post-transcriptionally.

Interleukin-10 inhibits lipopolysaccharide-induced tumor necrosis factor-α translation through a SHIP1-dependent pathway.

Production of the proinflammatory cytokine TNFα by activated macrophages is an important component of host defense. However, TNFα production must be tightly controlled to avoid pathological consequences. The anti-inflammatory cytokine IL-10 inhibits TNFα mRNA expression through activation of the STAT3 transcription factor pathway and subsequent expression of STAT3-dependent gene products. We hypothesized that IL-10 must also have more rapid mechanisms of action and show that IL-10 rapidly shifts existing TNFα mRNA from polyribosome-associated polysomes to monosomes. This translation suppression requires the presence of SHIP1 (SH2 domain-containing inositol 5'-phosphatase 1) and involves inhibition of Mnk1 (MAPK signal-integrating kinase 1). Furthermore, activating SHIP1 using a small-molecule agonist mimics the inhibitory effect of IL-10 on Mnk1 phosphorylation and TNFα translation. Our data support the existence of an alternative STAT3-independent pathway through SHIP1 for IL-10 to regulate TNFα translation during the anti-inflammatory response.

A pleckstrin homology-related domain in SHIP1 mediates membrane localization during Fcγ receptor-induced phagocytosis.

SH2 domain-containing inositol-5'-phosphatase-1 (SHIP1) inhibits inflammation by hydrolyzing phosphoinositide-3'-kinase generated membrane phosphatidylinositol-3,4,5-trisphosphate (PIP(3)). Bioinformatic analysis of SHIP1 from multiple species revealed a pleckstrin homololgy-related (PH-R) domain, which we hypothesize mediates SHIP1's association with the membrane, a requirement for its biological function. Recombinant murine SHIP1 PH-R domain was subjected to biophysical and biochemical analysis. Residues K370 and K397 were found to be important for PH-R domain association with membrane PIP(3). Wild-type PH-R domain bound PIP(3) with 1.9 ± 0.2 nM affinity, while the affinity of a K370A/K397A substituted mutant was too low to measure. Wild-type (but not the K370A/K397A substituted) full-length SHIP1 protein, reconstitutes normal inhibition of Fcγ receptor-mediated phagocytosis when introduced into SHIP1(-/-) murine macrophages, reducing the number of phagocytic events by 2-fold as compared to SHIP1(-/-) cells. In fact, the PH-R-mediated membrane interaction appears to be a major mechanism by which SHIP1 is recruited to the membrane, since the K370A/K397A substitution reduced the recruitment of both full-length SHIP1 and the PH-R domain by ≥2-fold. We have previously shown that SHIP1 enzyme activity can be targeted for therapeutic purposes. The current studies suggest that molecules targeting the PH-R domain can also modulate SHIP1 function.

Turnagainolides A and B, cyclic depsipeptides produced in culture by a Bacillus sp.: isolation, structure elucidation, and synthesis.

Two new cyclic depsipeptides, turnagainolides A (1) and B (2), have been isolated from laboratory cultures of a marine isolate of Bacillus sp. The structures of 1 and 2, which are simply epimers at the site of macrolactonization, were elucidated by analysis of NMR data and chemical degradation. A total synthesis of the turnagainolides confirmed their structures. Turnagainolide B (2) showed activity in a SHIP1 activation assay.

Differentiation of mouse embryonic stem cells into endoderm without embryoid body formation.

Pluripotent embryonic stem cells hold a great promise as an unlimited source of tissue for treatment of chronic diseases such as Type 1 diabetes. Herein, we describe a protocol using all-trans-retinoic acid, basic fibroblast growth factor and dibutyryl cAMP (DBcAMP) in the absence of embryoid body formation, for differentiation of murine embryonic stem cells into definitive endoderm that may serve as pancreatic precursors. The produced cells were analyzed by quantitative PCR, immunohistochemistry and static insulin release assay for markers of trilaminar embryo, and pancreas. Differentiated cells displayed increased Sox17 and Foxa2 expression consistent with definitive endoderm production. There was minimal production of Sox7, an extraembryonic endoderm marker, and Oct4, a marker of pluripotency. There was minimal mesoderm or neuroectoderm formation based on expression levels of the markers brachyury and Sox1, respectively. Various assays revealed that the cell clusters generated by this protocol express markers of the pancreatic lineage including insulin I, insulin II, C-peptide, PDX-1, carboxypeptidase E, pan-cytokeratin, amylase, glucagon, PAX6, Ngn3 and Nkx6.1. This protocol using all-trans-retinoic acid, DBcAMP, in the absence of embryoid bodies, generated cells that have features of definitive endoderm that may serve as pancreatic endocrine precursors.

Activation of SHIP via a small molecule agonist kills multiple myeloma cells.

OBJECTIVE: Multiple myeloma (MM) is a B-lymphocyte neoplasia that is presently incurable because the tumor cells become resistant to currently available drugs. The growth and survival signals resulting from interactions between the malignant clones and the bone marrow microenvironment are mediated chiefly through the phosphoinositide 3'-kinase/Akt kinase signaling pathway. Thus agents that can abrogate this pathway have great potential as targeted therapies. A novel approach in this regard is through activation of the Src homology 2-containing inositol 5'-phosphatase (SHIP), using the small molecule agonist, AQX-MN100. MATERIALS AND METHODS: The SHIP agonist AQX-MN100 was tested in vitro for its ability to inhibit DNA synthesis, induce apoptosis in MM cell lines, as well as inhibit phosphorylation of the kinases in the phosphoinositide 3'-kinase/Akt kinase cascade. The ability of AQX-MN100 to enhance the cytotoxicity of the current MM therapeutic drugs dexamethasone and bortezomib was also examined. RESULTS: We demonstrate herein that activation of SHIP using AQX-MN100 is sufficient to prevent growth and induce cytotoxicity of MM cell lines, while having no significant effects on nonhematopoietic cells lacking SHIP. AQX-MN100 also augments the effects of the established agents dexamethasone and bortezomib. CONCLUSION: These results provide the basis for the further study of small molecule SHIP activators to improve MM patient outcomes.

PTEN loss promotes mitochondrially dependent type II Fas-induced apoptosis via PEA-15.

Two distinct biochemical signals are delivered by the CD95/Fas death receptor. The molecular basis for the differential mitochondrially independent (type I) and mitochondrially dependent (type II) Fas apoptosis pathways is unknown. By analyzing 24 Fas-sensitive tumor lines, we now demonstrate that expression/activity of the PTEN tumor suppressor strongly correlates with the distinct Fas signals. PTEN loss-of-function and gain-of-function studies demonstrate the ability to interconvert between type I and type II Fas pathways. Importantly, from analyses of Bcl-2 transgenic Pten(+/-) mice, Pten haploinsufficiency converts Fas-induced apoptosis from a Bcl-2-independent to a Bcl-2-sensitive response in primary thymocytes and activated T lymphocytes. We further show that PTEN influences Fas signaling, at least in part, by regulating PEA-15 phosphorylation and activity that, in turn, regulate the ability of Bcl-2 to suppress Fas-induced apoptosis. Thus, PTEN is a key molecular rheostat that determines whether a cell dies by a mitochondrially independent type I versus a mitochondrially dependent type II apoptotic pathway upon Fas stimulation.

Small-molecule agonists of SHIP1 inhibit the phosphoinositide 3-kinase pathway in hematopoietic cells.

Because phosphoinositide 3-kinase (PI3K) plays a central role in cellular activation, proliferation, and survival, pharmacologic inhibitors targeting components of the PI3K pathway are actively being developed as therapeutics for the treatment of inflammatory disorders and cancer. These targeted drugs inhibit the activity of either PI3K itself or downstream protein kinases. However, a previously unexplored, alternate strategy is to activate the negative regulatory phosphatases in this pathway. The SH2-containing inositol-5'-phosphatase SHIP1 is a normal physiologic counter-regulator of PI3K in immune/hematopoietic cells that hydrolyzes the PI3K product phosphatidylinositiol-3,4,5-trisphosphate (PIP(3)). We now describe the identification and characterization of potent and specific small-molecule activators of SHIP1. These compounds represent the first small-molecule activators of a phosphatase, and are able to activate recombinant SHIP1 enzyme in vitro and stimulate SHIP1 activity in intact macrophage and mast cells. Mechanism of activation studies with these compounds suggest that they bind a previously undescribed, allosteric activation domain within SHIP1. Furthermore, in vivo administration of these compounds was protective in mouse models of endotoxemia and acute cutaneous anaphylaxis, suggesting that SHIP1 agonists could be used therapeutically to inhibit the PI3K pathway.

Proteasome-mediated proteolysis of the interleukin-10 receptor is important for signal downregulation.

The cytokine interleukin-10 (IL-10) is an important regulator of immune cell function, proliferation, and survival. The IL-10 receptor (IL-10R) consists of two subunits, IL-10R1 and IL-10R2, both belonging to the class II cytokine receptor superfamily. Like other members of the cytokine receptor superfamily, IL-10R stimulation leads to activation of Jak family kinases and Stat transcription factors. To identify additional signal transduction pathways used by the IL-10R, we purified 92-kDa and 100-kDa proteins that coprecipitated with IL-10R1 from IL-10-stimulated cells. Both proteins were found to be related to the 97-kDa subunit of the regulatory component of the 26S proteasome. Subsequent studies confirmed that the IL-10R1 undergoes ligand- dependent internalization and proteasome-mediated degradation. An IL-10R1 cytoplasmic domain mutant deficient for internalization exhibited prolonged signaling through Jak1 and Stat3, reinforcing the importance of receptor internalization for signal termination.

Glutathione depletion of stimulator cells inhibits responder T-cell immunogenicity in vitro and prolongs allograft survival in vivo.

BACKGROUND: Pretransplant donor-organ immunomodulation may attenuate allograft rejection by changing the redox state of donor cells. This study explored impact of donor-cell redox-state alteration by glutathione (GSH) depletion on graft immunogenicity. METHODS: Splenic and heart endothelial cells from Balb/c mice were treated with diethylmaleate (a GSH-depleting agent) and/or lipopolysaccharide to assess the impact of GSH depletion on alloreactivity by mixed lymphocyte reaction, endothelial cell adhesion by T-cell adhesion assay, intracellular adhesion molecule-1 expression by reverse transcriptionase-polymerase chain reaction, and nuclear factor-kappa B upregulation by electrophoretic mobility shift assay. Heterotopic heart transplants were performed as in vivo correlate. RESULTS: GSH depletion decreased endothelial cell and splenic cell alloreactivity, decreased endothelial cell intracellular adhesion molecule-1 expression through attenuation of nuclear factor-kappa B activity, decreased endothelial cell adhesion, and prolonged heterotopic heart transplant graft survival. CONCLUSIONS: GSH depletion may represent a significant immunomodulator of donor antigenicity to prevent transplant rejection.

Inhibition of the phosphatidylinositol 3'-kinase pathway promotes autocrine Fas-induced death of phosphatase and tensin homologue-deficient prostate cancer cells.

Rationally designed therapeutics that target the phosphatidylinositol 3'-kinase (PI3K) cell survival pathway are currently in preclinical and clinical development for cancer therapy. Drugs targeting the PI3K pathway aim to inhibit proliferation, promote apoptosis, and enhance chemosensitivity and radiosensitivity of cancer cells. The phosphatase and tensin homologue (PTEN) phosphatidylinositol 3'-phosphatase is a key negative regulator of the PI3K pathway. Inactivation of the PTEN tumor suppressor results in constitutive activation of the PI3K pathway and is found in approximately 50% of advanced prostate cancers, which correlates with a high Gleason score and poor prognosis. Inhibition of the PI3K pathway leads to apoptosis of prostate cancer cells; however, the precise mechanism by which this occurs is unknown. Here we report that apoptotic cell death of PTEN-deficient LNCaP and PC3 prostate cancer cells induced by the PI3K inhibitor LY294002 can be abrogated by disrupting Fas/Fas ligand (FasL) interactions with recombinant Fas:Fc fusion protein or FasL neutralizing antibody (Nok-1), or by expressing dominant-negative Fas-associated death domain. Furthermore, we find that apoptosis induced by expression of wild-type PTEN, driven by a tetracycline-inducible expression system in LNCaP cells, can be inhibited by blocking Fas/FasL interaction using Fas:Fc or Nok-1. These data show that apoptosis induced by blockade of the PI3K pathway in prostate tumor cells is mediated by an autocrine Fas/FasL apoptotic mechanism and the Fas apoptotic pathway is both necessary and sufficient to mediate apoptosis by PI3K inhibition.

Loss of PTEN is associated with progression to androgen independence.

BACKGROUND: Progression to a lethal androgen-independent (AI) stage of advanced prostate cancer is a critical clinical obstacle limiting patient survival. PTEN inactivation is frequently observed in advanced prostate cancer and correlates with a poor prognosis. However, the functional significance of PTEN inactivation in AI progression has not been demonstrated. METHODS: PTEN expression was examined in benign, hormone naïve and AI human prostate cancer specimens, and in recurrent AI Shionogi tumors. The effect of antisense oligonucleotide (ASO)-mediated PTEN downregulation in AI progression of the Shionogi tumor model was determined. RESULTS: Significantly reduced PTEN expression was observed in AI versus benign and hormone naïve prostate tumors. Seven of 14 AI Shionogi tumors exhibited marked downregulation or complete loss of PTEN. ASO-mediated PTEN inhibition reduced androgen-withdrawal induced regression of Shionogi tumors and accelerated AI progression. CONCLUSIONS: These data suggest that PTEN inactivation may play a role in progression to androgen independence.

Divergent mechanisms utilized by SOCS3 to mediate interleukin-10 inhibition of tumor necrosis factor alpha and nitric oxide production by macrophages.

The cytokine interleukin-10 (IL-10) potently inhibits macrophage function through activation of the transcription factor STAT3. The expression of SOCS3 (suppressor of cytokine signaling-3) has been shown to be induced by IL-10 in a STAT3-dependent manner. However, the relevance of SOCS3 expression to the anti-inflammatory effect of IL-10 on macrophages has been controversial. Through kinetic analysis of the requirement for SOCS3 in IL-10 inhibition of lipopolysaccharide (LPS)-stimulated tumor necrosis factor-alpha (TNFalpha) transcription and translation, SOCS3 was found to be necessary for TNFalpha expression during the early phase, but not the late phase of IL-10 action. SOCS3 was essential for IL-10 inhibition of LPS-stimulated production of iNOS (inducible nitric-oxide synthase) protein and nitric oxide (NO). To determine the domains of SOCS3 protein important in mediating these effects, SOCS3-/- macrophages were reconstituted with SOCS3 mutated for the SH2, KIR, SOCS box domains, and tyrosines 204 (Tyr204) and 221 (Tyr221). The SH2 domain, SOCS box, and both Tyr204 and Tyr221 were required for IL-10 inhibition of TNFalpha mRNA and protein expression, but interestingly the KIR domain was necessary only for IL-10 inhibition of TNFalpha protein expression. In contrast, Tyr204 and Tyr221 were the only structural features of SOCS3 that were necessary in mediating IL-10 inhibition of iNOS protein expression and NO production. These data define SOCS3 as an important mediator of IL-10 inhibition of macrophage activation and that SOCS3 interferes with distinct LPS-stimulated signal transduction events through differing mechanisms.